-Galla S Kiran Kumar,Bureau Chief Telagana (Andhra Pradesh)
As part of the Polavaram project, the guide bond built at a cost of Rs. 81 crore has collapsed within a year of its construction. As a part of the project, a spillway constructed to control the flood flow and store water in the reservoir was constructed as a guide bond for protection.
If the guide bund collapses.. It is worse that CM Jagan says it is a minor problem. The
construction intended to protect the key spillway in Polavaram is
a structure that controls the flow speed regardless of whether
the guide bund was designed and built by Megha Company . Do you have to pay that much again? – Amaravati
As part of the Polavaram project, the guide bond built at a cost of Rs. 81 crore has collapsed within a year of its construction. As a part of the project, a guide bund was constructed for the protection of the spillway built to control the flood flow and store water in the reservoir. When there is a heavy flood in Godavari, due to the speed of the flow, the pressure on one side of the spillway does not increase. A situation where such a key structure collapses and collapses is causing awe in engineering circles. Anyone who examines this will find the error due to two reasons. One, the construction of the guidebund must be flawed in design itself. Or maybe it’s not built to that design. This design was created by Megha Engineering Company, which undertook the construction of the project. Megha Company has approved the guidelines and built the guidelines!
What is the need for a guideline?
As Chief Minister Jagan commented, Guidebund is not a small task. Not even a small bundle. This is one of the key structures of the project. The construction of the Polavaram project is different. It is not a project to control the water and turn it into a reservoir by constructing a spillway in the natural flow path of Godavari and installing gates. Due to the soil and geophysical conditions here, the construction area of the spillway was shifted to the hilly area on the river bank. To that extent, the design was decided to change the flow path of Godavari. The river was diverted from its natural course. For this, some approach channel has been dug and some more needs to be dug. A spillway was constructed in a hilly area near the natural course of the river. Later a spill channel was dug and the river was rejoined in its natural course.
* Along with the spillway, an upper coffer dam has already been constructed on the natural course of Godavari at a height of 44 meters. Due to this, the flood is diverting from the natural course of the river towards the approach channel and spillway. The research institutes that examined the flow pattern concluded that the water velocity is high towards the left flank of the spillway. It has been found that eddies can form here and have a negative effect. To prevent this, the experts of the Central Water and Power Research Institute in Pune designed and studied a 3D model of the project.
* On the left side of the spillway, it was found that the water was swirling during the flood, and on the left flank, there was a flow of 13.6 meters per second. It was concluded that the velocity in the center of the spillway was 9.2 meters per second, which was dangerous. Here several recommendations have been made to ensure smooth flow of the flood without any adverse effects. At the mouth of the approach channel diverting the Godavari, the 450 meter wide excavated road should be increased from 550 to 660 meters. A 500 meter long guide bund should be constructed on the left side of the spillway adjacent to it and on the left side of the approach channel.
* According to the report of the Central Hydropower Research Center, if a guidebund is constructed, huge eddies can be avoided on the left flank of the spillway and the flow speed will be reduced. It was concluded that if a guidebund is constructed and changes are made in the approach channel, the flood velocity will decrease to 4 meters per second on the left flank and 5.5 meters per second in the middle.
* Means.. Guideband is the key structure for spillway protection in Polavaram. Moreover, it was not less spent on its construction. 81 crores together.
Is it a small comment?
Chief Minister Jagan’s role in reviewing the progress of the Polavaram project and alerting the authorities is limited. There are seldom reviews of the project. The supervision of the authorities is questionable. Outsiders are not allowed in the Guidebund area. Officials are not saying why the pony and guideband were damaged. Accepting the loss caused by ‘defect in design or construction’. ‘We did everything right. Sometimes this happens. We have informed the Polavaram Authority and Central Jal Sangam. In two or three days, experts from the center will come and resolve it.’
How is the guideline constructed?
Megha Engineering Company prepared the designs after the Central Hydropower Research Center recommended the need for a guideline. The construction was taken up with the approval of CWC.
* It was decided to develop the Guidebund foundation strata (below) with stone columns and cut-off type construction with diaphragm wall on flood water side.
* The RCC diaphragm wall built on the flood flow side is 1.5 meters thick. The height of RCC is from minus 5 meters to +25 meters. That is, 500 meters long on the side of the river flow from underground to 25 meters high (total 30m) was built.
* Then the guidebund was built with stones. From the level of +23.68 meters to +51.32 meters it is built with stones. It is 117.28 meters at the bottom and 6 meters wide at the top. It is said that the results of all the tests done on the geophysical conditions before the designs and during the construction have come as expected. However, the authorities are not saying why it has collapsed.
‘Enadu’ discussed with experienced engineers and experts on Polavaram about the way the guide bond collapsed. What are their opinions?
Things like this happen!
When the engineers were saying that they would have to build from scratch in place of the sagged guide bund, it was surprising that Chief Minister Jagan dismissed this as a small issue. The Chief Minister, who visited the Polavaram project on Wednesday, responded to the destruction of the guidewall. Officials say that the designs of the central water body were approved by the CWC and the work was done accordingly. Small problems naturally occur in project constructions. Officials proceed by observing and repairing them. “There is an unfortunate situation in the state where a small problem is seen as a disaster,” he said. It is noteworthy that Jagan considers this as a small problem if the structure meant to protect the vital spillway collapses. Further action is not mentioned.
Is it a loss of Rs.
The cost of this guidebund and retaining wall type construction is Rs.81 crores. Engineering officials are not sure whether it will be enough to fix the guidebund as both are sagging. It is said that the extent of damage to the retaining wall and the condition of the stonework should be studied. The authorities do not believe that repairs can be made. It is said that if the entire Bund is to be built again, the expenditure will increase.
There may be defects in construction and quality
– Retired Superintendent Engineer
It is primarily believed that the reasons for the sagging of the guide bond are due to defects in design and construction quality. There may be a defect in the work done to increase the density of the soil where it is built. There may also be defects in the work done with stone columns. The depth taken may not be sufficient for diaphragm wall construction. Built from a depth of -5 meters in the ground. That may not be enough. There are doubts about the quality of the stones used in the rock fill dam. We have to find out where the stones were brought from. It should be seen whether the construction has been done according to the results of the soil investigation.
Doubts on Design
– Key Engineering Officer
Mainly there are doubts about the design. These are black soils. This type of construction is not suitable. Officials of DPM (Design Department) say that they identified this matter first. It is said that the matter was ignored after the approval of the CWC. It is being discussed that the approvals were received very quickly at the CWC after the design was submitted.
Construction style should be changed
– Retired Chief Engineer
Officials say that everything was done properly. But, Rock Phil Dam’s style of construction should have changed. Generally the pre stone slope is in the ratio of 2:1. Apart from that, if 3:1 had been taken up, some burden on the slope would have been reduced. (When asked if gabion type structure would have been sufficient) The dam design committee approved the construction of gabion type embankments on the right side of the spill channel. There is an opportunity to build it. Here it is said that the design was approved after many tests and observations.
